Ink jet printheads made from a piezoelectric material are used to selectively eject ink droplets onto a receiver to form an image. Within the printhead, the ink may be contained in a plurality of channel members and energy pulses are used to actuate the printhead channel members causing the droplets, which form the reservoirs of ink to be ejected on demand or continuously, through an orifice plate over the channel member.
In one representative configuration, a piezoelectric ink jet printing system includes a body of piezoelectric material defining an array of parallel open topped channel members separated by walls. In the typical case of such an array, the channel members are micro-sized and are arranged such that the spacing between the adjacent channel members is relatively small. The channel walls have metal electrodes on opposite sides thereof to form shear mode actuators for causing droplets to expel from the channel members. An orifice defining structure includes at least one orifice plate defining the orifice through which the ink droplets are ejected, and is bonded to the open end of the channel members. In operation of piezoelectric printheads, ink is directed to and resides in the channel members until selectively ejected therefrom. To eject an ink droplet through one of the selected orifices, the electrodes on the two side wall portions of the channel in operative relationship with the selected orifice are electrically energized causing the side walls of the channel to deflect into the channel and return to their normal undeflected positions when the applied voltage is withdrawn. The driven inward deflection of the opposite channel wall portions reduces the effective volume of the channel thereby increasing the pressure of the ink confined within the channel to force few ink droplets, 1 to 100 pico-liters in volume, outwardly through the orifice. Piezoelectric ink jet printheads are described in detail in U.S. Pat. Nos. 5,598,196; 5,311,218; 5,365,645, 5,688,391, 5,600,357, and 5,248,998.
The use of piezoelectric materials in ink jet printheads is well known. Most commonly used piezoelectric material is lead-zirconate-titanate (PZT) ceramic, which is used as a transducer by which electrical energy is converted into mechanical energy by applying an electric field across the material, thereby causing the piezoelectric ceramic to deform. The degree of deformation of the piezoelectric materials depend on several factors, including chemical composition, grain size of the material, and the electrode configuration of the transducers.
Under previous methods of making piezoelectric ink jet printheads, a dense sintered slab of piezoelectric ceramic such as PZT in which channel members/grooves are to be formed is poled. Poling makes the material piezoelectrically deflectable or "active", by imparting a pre-determined voltage widthwise across the piezoelectric ceramic slab in a selected poling direction of the internal channel side wall sections later to be created in the poled ceramic body section by forming a spaced series of parallel grooves in channel members. These grooves in the channel members are generally formed by sawing, laser cutting or etching process. This current process of poling a bulk piezoelectric ceramic material and later fabricating micro-sized channel members by sawing or other processes is discussed in detail in U.S. Pat. Nos. 5,227,813 and 5,028,937, and in EP 827833. This process of forming channel members is not only time consuming and expensive, but also is amenable to many defects generated during cutting the channel members or forming the channel members thereby reducing the throughput and increasing the unit manufacturing cost. Furthermore, mechanical damages caused during sawing or laser cutting also are detrimental to the piezoelectric characteristics of the material.